The present invention relates to highly active and stable esters of 17.alpha.-ethynyl-7.alpha.-methyl-1,3,5(10)-estratriene-1,3,17.beta.-triol , to processes for the preparation thereof and to pharmaceutical compositions containing the same.
German Pat. No. 1,593,509 discloses 1-hydroxy-7.alpha.-methylestradiol derivatives of the general formula ##STR1## wherein R.sub.1 and R.sub.2, which can be the same or different, are hydrogen, lower alkyl, a saturated oxygen-heterocyclic residue, or a physiologically acceptable acid residue, and
R.sub.3 is hydrogen or saturated or unsaturated lower alkyl.
These compounds possess valuable therapeutic properties. They are distinguished, in particular, by strong estrogenic and ovulation-inhibiting activities. A preferred compound of the German patent is 17.alpha.-ethynyl-1,3-diacetoxy-7.alpha.-methyl-1,3,5(10)estratrien-17.bet a.-ol (I). During clinical testing also, it proved to be a very strong estrogen for its effectiveness on the endometrium. Compared to 17.alpha.-ethynylestradiol, compound I has an activity which is about 10 times higher.
With such highly effective active agents, correspondingly low doses only need be used in preparations. Accordingly, and unfortunately, especially high stabilities are required of the active agents. It has now been found that compound I, in the desired, low dosage in which it is used in a preparation, i.e., 0.001-0.05 mg, is unstable during exertion of a dry temperature load of up to 60.degree. C. over a period of 2-7 months.
Consequently, it is desired to have a highly effective such agent which also has high stability, e.g., storage stability.